Initiate mid-call probing even if estimated bitrate is at max configured bitrate.

webrtc/modules/congestion_controller/probe_controller.cc

Index: webrtc/modules/congestion_controller/probe_controller.cc
diff --git a/webrtc/modules/congestion_controller/probe_controller.cc b/webrtc/modules/congestion_controller/probe_controller.cc
index e66f0cec3dd377aaeab743bc2d31c6df0944f1a6..373b268d2cdf591cae0a5d368f648dee88cc8033 100644
--- a/webrtc/modules/congestion_controller/probe_controller.cc
+++ b/webrtc/modules/congestion_controller/probe_controller.cc
@@ -72,6 +72,8 @@ void ProbeController::SetBitrates(int64_t min_bitrate_bps,
     start_bitrate_bps_ = min_bitrate_bps;
   }
 
+  // The reason we use the variable |old_max_bitrate_pbs| is because we
+  // need to set |max_bitrate_bps_| before we call InitiateProbing.
   int64_t old_max_bitrate_bps = max_bitrate_bps_;
   max_bitrate_bps_ = max_bitrate_bps;
 
@@ -85,10 +87,11 @@ void ProbeController::SetBitrates(int64_t min_bitrate_bps,
       break;
 
     case State::kProbingComplete:
-      // Initiate probing when |max_bitrate_| was increased mid-call.
-      if (estimated_bitrate_bps_ != kExponentialProbingDisabled &&
-          estimated_bitrate_bps_ < old_max_bitrate_bps &&
-          max_bitrate_bps_ > old_max_bitrate_bps) {
+      // If the new max bitrate is higher than the old max bitrate and the
+      // estimate is lower than the new max bitrate then initiate probing.
+      if (estimated_bitrate_bps_ != 0 &&
+          old_max_bitrate_bps < max_bitrate_bps_ &&
+          estimated_bitrate_bps_ < max_bitrate_bps_) {
         // The assumption is that if we jump more than 20% in the bandwidth
         // estimate or if the bandwidth estimate is within 90% of the new
         // max bitrate then the probing attempt was successful.